1. Field of the Invention
This invention relates to oil and gas drilling, and more particularly to apparatus and methods for reliably transmitting information along downhole drilling strings.
2. Background of the Invention
In the downhole drilling industry, MWD and LWD tools are used to take measurements and gather information with respect to downhole geological formations, status of downhole tools, conditions located downhole, and the like. Such data is useful to drill operators, geologists, engineers, and other personnel located at the surface. This data may be used to adjust drilling parameters, such as drilling direction, penetration speed, and the like, to accurately tap into oil, gas, or other mineral bearing reservoirs. Data may be gathered at various points along the drill string. For example, sensors, tools, and the like, may be located at or near the bottom hole assembly and on intermediate tools located at desired points along the drill string.
Nevertheless, data gathering and analysis do not represent the entire process. Once gathered, apparatus and methods are needed to rapidly and reliably transmit the data to the earth's surface. Traditionally, technologies such as mud pulse telemetry have been used to transmit data to the surface. However, most traditional methods are limited to very slow data rates and are inadequate for transmitting large quantities of data at high speeds.
In order to overcome these limitations, various efforts have been made to transmit data along electrical or other types of cable integrated directly into drill string components, such as sections of drill pipe. In such systems, electrical contacts or other transmission elements are used to transmit data across tool joints or connection points in the drill string. Nevertheless, many of these efforts have been largely abandoned or frustrated due to unreliability and complexity.
For example, one challenge is effectively integrating a transmission line into a downhole tool, such as a section of drill pipe. Due to the inherent nature of drilling, most downhole tools have a similar cylindrical shape defining a central bore. The wall thickness surrounding the central bore is typically designed in accordance with weight, strength, and other constraints imposed by the downhole environment. In some cases, milling or forming a channel in the wall of a downhole tool to accommodate a transmission line may critically weaken the wall. Thus, in certain embodiments, the only practical route for a transmission line is through the central bore of the downhole tool.
At or near the box end and pin end of the downhole tool, a transmission line may be routed from the central bore through the tool wall. This may be done for several reasons. First, the box end and pin end are typically constructed with thicker walls to provide additional strength at the tool joints. This added thickness is many times sufficient to accommodate a channel without critically weakening the wall. Second, transmission elements are typically installed in the box end and pin end to transmit information across the tool joints. These transmission elements are typically embedded within recesses formed in the box end and pin end. Thus, channels are needed in the box end and pin end to provide a path for the transmission line between the transmission elements and the central bore of the downhole tool.
Thus, what are needed are apparatus and methods for installing channels in the box end and pin end of downhole tools to provide routes for transmission lines traveling between transmission elements and the central bore.
What are further needed are improved apparatus and methods for providing a smooth path for a transmission line routed through a downhole tool to prevent kinking or other damage.
What are further needed are improved apparatus and methods for effectively drilling or otherwise forming channels in the box end and pin end of a downhole tool.
Finally, what are needed are apparatus and methods to minimize the expense and labor required to install these channels in the box end and pin end of a downhole tool.